Note: Descriptions are shown in the official language in which they were submitted.
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HIGH THROUGHPUT ELECTROPHYSIOLOGY SYSTEM
RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional patent application
serial
number 60/555,756, filed on March 23, 2004, which is hereby incorporated by
reference in its entirety.
FIELD OF INVENTION
[0002] This invention relates to a high throughput device capable of
detecting,
measuring, and recording electrical activity in large numbers of neurological
tissues
and slices. In one variation, the device may be considered a high-throughput
electrophysiology recording system, particularly suitable for use in a
laboratory.
BACKGROUND OF INVENTION
[0003] Over the past decade or more, medical investigators have actively
pursued
the use of nerve cell and neuronal tissue electrical activity in assessing the
effects of
psycho-active materials on those tissues. When nerve cells are active, that
activity is
evidenced by generation of a potential or a voltage. This potential arises
from changes
in ion concentration inside and outside the cell membrane accompanied by a
change in
ion permeability in nerve cells. Measuring of this potential change and the
ion
concentration change (that is, the ion current) near the nerve cells with
electrodes
allows detection of nerve cell or tissue activity.
[0004] Early worl~ers in the field measured this cell activity potential by
inserting
a glass electrode into an area containing cells to measure extracellular
potential.
When evolved potential due to stimulation was measured, a metal electrode for
stimulation was inserted together with a glass electrode for recording.
However, the
insertion of these electrodes carried with it the possibility of causing cell
damage and
long term measurement was difficult to do. In addition, space restrictions and
the
need for operating accuracy then made multipoint simultaneous measurements
difficult to achieve.
[0005] U.S. Pat. No. 5,563,067 issued October 8, 1996; U.S. Pat. No. 5,810,725
issued September 22, 1998; U.S. Pat. No. 6,132,683 issued October 17, 2000;
U.S.
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Pat. No. 6,151,519 issued November 21, 2000; U.S. Pat. No. 6,281,670 issued
August
28, 2001; U.S. Pat. No. 6,288,527 issued September 2, 2001; and U.S. Pat. No.
6,297,025 issued October 2, 2001, (each to Sugihara et al and incorporated by
reference) describe a device employing a planar electrode having a large
number of
microelectrodes on an insulated substrate that first allowed multi-point
simultaneous
measurements of potential change at a number of points This device had small
electrode-to-electrode distances and allowed long-term measurement of neuronal
electrical activity.
[0006] One commercially available device made according to the listed patents
incorporated an integrated cell holding instmunent having a planar electrode
assembly
having a plurality of microelectrodes and their respective lead-ins positioned
on the
surface of a glass plate. The electrode assembly often included half split
holders for
fixing the planar electrode by holding it from the top and bottom. The holders
were
often positioned upon a printed circuit board
[0007] A typical planar electrode assembly was made up of a transparent Pyrex
glass sheet having a thickness of 1.1 mm and a size of 50X50 mm. In the center
of
this substrate, 64 microelectrodes were formed in an 8X8 matrix. Each
microelectrode was connected to a conductive lead-in. The exemplified
electrodes
were each 50X50 ~.m square (area 25X102 ~m2) and the center-to-center distance
between adjacent electrodes was 150 ~.m. Each side of the substrate had 16
contact
points with a pitch of 1.27 mm, totaling 64 exterior contacts. These electric
contact
points were connected to the microelectrodes in the center of the substrate in
a 1 to 1
correspondence.
[0008] These planar electrodes were manufactured in the following fashion. ITO
(indium tin oxide), for example, was applied to form a layer of 150 nm thick
on the
surface of the glass plate used as the substrate. A conductive array was then
formed
using a photoresist and etching. On top of this layer, a negative
photosensitive
polyimide was applied to form a layer about 1.4~,m in thickness and then
formed into
an overlying insulative film. The ITO layer was then coated with nickel (15 to
500
nm thick) and gold (16 to 50 nm thiclc) in the microelectrode region and at
the
peripheral electric contact points. A cylindrical polymeric (e.g_,
polystyrene) frame
having an inner diameter of 22 mm, an outer diameter of 26 mrn, and a height
of 8
mm was then stuclc to the center of the glass plate using a silicone adhesive
to form a
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cell holding part around the central part of 64 microelectrodes. The inside of
this
polystyrene frame was to be filled with solutions containing, e.g.,
chloroplatinic acid,
lead acetate, and hydrochloric acid. Application of a modest electric current
deposited
platinum black gold plating of the microelectrodes.
[0009] The half split holders were often molded of a resin having an arm
portion
for holding the edge of the planar electrode. Also, the upper portion of the
holder was
pivotable by an axis pin. The upper portion of the holder typically was
equipped with
control fixtures having 16 X 4 pairs of contacts. The contacts in the upper
holder
correspond to electric contact points of the planar electrode and were formed
of a
spring of metal such as BeCu coated with Ni and Au.
[0010] The pin parts protruding from the upper holder are alternately arranged
so
that the 16 pieces of the pin part protruding from the upper holder are lined
in two
staggered rows. This pin part is connected to a connector mounted on a printed
circuit
board used for connection with the outside.
[0011] Also, the spring contacts protrude from the bottom face of the upper
holder. All contact the planar electrode with a predetermined contact pressure
resulting in an electrical connection having only small contact resistant e.
[0012] The printed circuit board serves not only for fixing the assemblies of
the
planar electrode and the holders but also provides an electrical connection
(via a
connector) to the outside, starting from the microelectrode of the planar
electrode, via
the conductive pattern, via the electric contact point, to the contact.
Furthermore, the
printed circuit board facilitates handling procedures, for example, in
installation to the
measurement apparatus.
[0013] The printed circuit board comprises a glass epoxy substrate having
double-
faced patterns and connectors at four parts around a circular opening formed
in the
center.
[0014] The printed circuit board usually has an edge part on each side with
electric
contact points to/on a double faced connector edge. For the purpose of
assuring
mechanical fixation, the upper holder can be fixed to the printed circuit
board using,
e.g., a clamp.
[0015] A configuration of a cell potential measurement apparatus using the
above-
configured integrated cell holding instrument includes an optical observation
device
such as an inverted microscope for optical observations of cells or tissues
placed in the
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integrated cell holding instrument. The system may include one or more
computers
including a device for providing a stimulation signal to the cells and a
device for
processing an output signal from the cells. Finally, the device may have a
cell
culturing means for maintaining a suitable culture medium for the cells.
[0016] In addition to the inverted microscope a camera may also be included or
used in place of a microscope. The system may include an image filing device.
The
camera may be a SIT camera. A SIT camera is a general term used for cameras
which
apply a static induction transistor to an image pickup tube, and a SIT camera
is a
representative example of very sensitive cameras.
[0017] A typical computer was a personal computer (for example, compatible
with
WINDOWS) having an A/D conversion board and measurement software. The A/D
conversion board includes an A/D converter and a D/A converter. The A/D
converter
has 16 bits and 64 channels, and the D/A converter has 16 bits and 8 channels.
[0018] The earlier measuring software included software for determining
conditions needed for providing a stimulation signal or recording conditions
of an
obtained detection signal. With this type of software, the computer was
capable of
structuring stimulation signals to the cells and processing the detected
signal from the
tissues or cells, and also was capable of controlling the optical observation
devices
(the SIT camera and the image filing device) and the cell culturing means.
[0019] The earlier software was reasonably flexible in that complicated
stimulation conditions were possible (e.g., by drawing a stimulation waveform
using
the computer). The recording conditions included 64 input channels, a sampling
rate
of 10 kHz, and continuous recording over several hours. Selection of an
electrode
providing a stimulation signal or an electrode for a detection signal was
specified, e.g.,
manually or using a computer mouse or pen. Also, various conditions such as
temperature, pH of the cell culturing fluid, etc., were displayable.
[0020] The software provided a recording screen displaying a spontaneous
action
potential or an evoked potential detected in real-time at a maximum of 64
channels.
The recorded or evoked potential was displayed on top of a microscope image of
the
tissue or cells. When the evolved potential was measured, the whole recording
waveform was displayed. When the spontaneous action potential was measured,
the
recording waveform was displayed only when an occurrence of spontaneous action
was detected by a spilve detection function using a window discriminator or a
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waveform discriminator. When the recording waveform was displayed, measurement
parameters (e.g., stimulation conditions, recording conditions, temperature,
pH) at the
time of recording was simultaneously displayed in real-time.
[0021] The software included data analysis, e.g., FFT analysis, coherence
analysis,
or another analysis software. In addition, the software had other
functionalities, such
as a single spike separation using a waveform discriminator, a temporal
profile display
function, a topography display function, and an electric current source
density analysis
function. Results of these analyses were displayable on top of the microscope
image
stored in the image filing device.
[0022] When a stimulation signal was emitted from the above-configured
computer, the stimulation signal was forwarded by way of a D/A converter and
an
isolator to the cells or tissues. An evolved potential arising between
microelectrodes
and a ground level (potential of culture solution) is routed to the computer
via 64
channels of a sensitized amplifier (for example, "AB-610J" manufactured by
NIHCrN
KODEN CO., LTD.) and an A/D converter. The amplification factor of the
amplifier
was 100 dB, and the frequency band was from 0 to 10 kHz. However, when an
evoked potential by a stimulation signal was measured, the frequency band was
selected to be from 100 Hz to 10 kHz using a low cut-off filter.
[0023] The tissue or cell culturing component had a temperature adjuster,
circulator for culture solution, and supply of mixed gas of air and carbon
dioxide.
[0024] Another form of the stimulation signal was a bipolar, constant voltage
pulse having a pair of positive and negative pulses for eliminating artifacts,
that is, for
preventing DC components from flowing. A preferred stimulation signal was a
positive pulse with a pulse width of 100 q s, an interval of 100 ~,s, and a
negative pulse
of 100 ~s. The peak electric current of the positive-negative pulse was in the
range of
30 to 200 ~.A.
[0025] The cell culturing means, when placed in the measurement apparatus,
enabled continuous measurement over a long period of time. Alternatively, the
integrated cell holding instrument allowed culturing separately from the
measurement
apparatus.
[0026] By using the above-mentioned cell potential measurement apparatus,
nerve
cells and organs were cultured on the integrated cell holding instalment and
the
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potential change accompanied by activities of the nerve cells or nerve organs
measured. The cerebral cortex section of rats were often used as nerve tissue.
[0027] Despite the flexibility of this device and the associated software, the
overall ability of the earlier devices to provide high throughput sampling and
selection
of adaptive testing regimes was nonexistent.
[0028] There has been considerable effort to develop higher throughput methods
and devices for electrophysiological recording from cells. These are
particularly
important in drug development where hundreds or thousands of compounds are to
be
electrophysiologically tested against cells or tissues. Recent developments in
this
field include high-throughput whole cell clamping using planar electrode, auto
patch
clamping using robotics, and high-throughput oocyte voltage clamping using
robotics.
These so-called cell based electrophysiological assays will definitely
accelerate early
stages of the drug development pipeline, however, tissue based (or slice)
physiology is
still necessary to determine psycho-active effects in intact tissues and to
understand
the compounds' mechanism of action. Dispersed cells are comparatively easier
to
handle, because they can be handled as solutions. Many types of dispensers are
available to transfer cells. In contrast, nerve tissues and slices are very
difficult to
handle and are not homogeneous. The characteristics of tissues and slices
require
expert physiologist to run even simple experiments and also inhibit developing
higher
throughput system.
[0029] Recent development of planar electrode array systems have made slice
physiology experiments somewhat more available to less spilled researchers by,
for
example, removing steps such as electrode preparation and searching for
stimulating
and recording sites. However, it still generally requires one physiologist to
operate the
system.
(0030] The device and procedures described here allow computer-controlled
switching of electrode stimulation sites. In earlier systems, even in those
where it is
possible to stimulate from different sites, a human operator has been needed
to move a
physical connection (using a cable or similaa- hardware) from one site to
another. This
process is illustrated in Figure 1.
[0031] As shown in Figure l, tissue slice physiology experiments have three
main
steps: (l.) an operator places the selected brain slice on the mufti-electrode
probe (1-2
minutes) (2.) the operator and the computer select the stimulation sites and
configure
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the stimulation parameters (10 minutes). This step consists of repeating the
following
two sub-steps: (a.) the software stimulates brain slice, captures and analyzes
data, and
displays results to the operator; and (b.) the operator makes a change to the
stimulation
site on the slice and adjusts stimulation parameters. Finally, in step (3.),
the
experiment is conducted which can take, e.g., between 60 and 120 minutes.
(0032] Once appropriate stimulation sites on the slice and stimulation
parameters
have been found, it is possible to automate the running of an experiment by
using
specialized software and expert systems technology. However, without having a
computer-controller hardware allowing the arbitrary selection of stimulation
sites, step
(2.) above cannot be automated.
[0033] Indeed, the number of experiments that can be run by a single operator
is
limited by the length of time required to carry out steps (1) and (2). This is
illustrated
in Figure 2, where 'O' represents the time to physically place the brain slice
on the
experimental setup, 'C' represents the time required to select and otherwise,
to
configure the stimulation site.and stimulation parameters, and 'E' represents
the time
to execute the experiment. As shown in Figure 2, selection of the stimulation
sites
and parameters are performed manually by the operator. This significantly
impedes
experiment throughput.
[0034] None of the commercially available systems provide for automation of
the
configuration step as described herein.
SUMMARY OF THE INVENTION
[0035] A system for monitoring electrophysiological information comprises at
least one muhti-electrode probe for monitoring and for stimulating tissue
sites of a
tissue sample placed on the probe. The system additionally includes a
controller
configured to select the tissue sites to be monitored and stimulated. In one
variation
of the invention, the controller is configured to automatically select the
tissue sites to
be monitored and stimulated.
[0036] The system may also comprise an amplifier module that is associated
with
each probe. In one variation the amplifier module is configured to amplify
electrical
signals evoked from the tissue sites. In another variation, the amplifier
module is
configured to distribute stimulation signals to the electrodes of the
associated probe.
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The amplifier may thus work in combination with the controller to manage the
probes
and electrodes.
[0037] The controller may be configured to select a wide variety of
stimulating
signals and tissue sites. In one variation, different voltage potentials are
applied to the
tissue sites. In another variation, a constant voltage potential is applied to
different
sets of electrodes. The stimulation signal can be switched fzom a first tissue
site to
second tissue site within a predetermined time period such as, for example,
0.5 to 2.5
ms. The stimulation signal may be time modulated such that evolved electrical
signals
corresponding to each stimulation signal may be separately monitored or
recorded.
[0038] The system may further comprise a computer comlected to the controller.
The computer may serve a variety of functions and is typically adapted to
program the
controller to automatically select tissue sites to be monitored and to deliver
a
preselected stimulation signal to an electrode set. The computer may also
receive and
record the electrical signals arising from the monitored tissue sites. Such
signals
include electrical signals evoked from tissue sites being stimulated as well
as
spontaneous action signals arising from tissue sites receiving little (or no)
electrical
stimulus. Indeed, a tissue site may be monitored that presents no electrical
activity.
[0039] The probe may vary in size and structure. In on_e variation, the probe
comprises a well having a planar base portion. The well is adapted to contain
a tissue
slice such as a brain tissue slice of a rat. The base portion supports the
plurality of
electrodes. There may be greater than 16 or perhaps, greater than 64
electrodes
associated with each probe. Additionally, multiple probes znay be connected to
the
controller such that multiple experiments may be run in parallel.
[0040] A method for monitoring electrophysiological information comprises (a.)
placing a sample of tissue on a mufti-electrode probe; (b.) selecting a first
set of
electrodes to monitor electrical activity of the tissue;(c.) automatically
selecting a
second set of electrodes to monitor electrical activity of the tissue; and
(d.)
monitoring the electrical activity. The tissue may be a tissue slice such as a
brain slice
of a mammal.
[0041] In a variation of the invention, the method further comprises selecting
tissue sites to be stimulated with stimulation signals. The stimulation
signals may be
varied or identical. Also, the tissue sites or locations to receive
stimulation signals
may be varied. The first stimulating signal may be applied prior,
simultaneous, or
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subsequent to the application of a second stimulating signal. W one variation,
at least
64 stimulation signals are sequentially applied to different sites of the
tissue sample.
[0042] The step of selecting electrodes to monitor may be carried out using a
controller. The controller may also be configured to select the stimulation
signals and
to select the tissue sites to be stimulated.
[0043] The method may additionally comprise the step of amplifying each signal
monitored. An amplifier module may be provided to amplify the evoked signals
as
well as to distribute the selected stimulation signal to selected electrodes
of the probe.
[0044] In one method, tissue samples are placed in a plurality of mufti
element
probes that are collectively managed by a controller. An amplifier module as
described above may be provided to manage each probe. The amplifier module
distributes stimulation signals selected by a controller to each probe and
each
electrode of that probe. In this manner, a plurality of tissue samples may be
interrogated in parallel and automatically.
[0045] Another electrophysiological information monitoring system comprises at
least one probe means for monitoring electrical activity of one or more tissue
sites of a
tissue sample and a control means connected to the probe means. The probe
means
generally comprises a plurality of multielectrodes. The control means is
configured to
automatically select electrodes for monitoring tissue sites. The control means
may
also be configured to select electrical stimulation signals to send to the
probe means.
Also, an amplifier means may be provided for each probe means such that
electrical
signals sensed from each microelectrode can be amplified. The amplifier means
may
also be configured to distribute the stimulation signals from the controller
to the
microelectrodes of the probe means. The system may also comprise a computer
connected to the control means to supply commands to the control means for
monitoring and stimulating the tissue sites. The computer may also be
configured to
monitor and/or record the electrical signals from the tissue sites being
monitored.
[0046] In another variation of the invention, a system for monitoring
electrophysiological information comprises a plurality of probes each adapted
to hold
a tissue slice. The probes include a plurality of electrodes that can monitor
electrical
activity of tissue sites of the tissue slice when the tissue slice is placed
on the probe.
The system further includes a daughter amplifier module for each probe. The
daughter amplifier module is adapted to amplify signals arising or evolved
from the
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tissue sites. The system further includes a plurality of daughter controllers
to manage
the daughter amplifier devices. A primary controller is configured to manage
all the
daughter controllers.
[0047] Aspects of the invention may vary. The probe may comprise at least 16
electrodes. In another variation, the probe comprises at least 64 electrodes _
The
system may also comprise between 4-10 probes for each daughter controller.
[0048] An integrated housing may contain the controllers and amplifiers.
However, the probes are typically separated from the housing. Also, a computer
may
be connected to the primary controller. The computer is configured to provide
instructions to the primary controller to select the electrical stimulation
signals as well
as to determine which tissue sites shall be monitored. The controller may be
configured to time-multiplex the stimulation signals. In this manner, many
tissue
sample experiments may be run in parallel and analyzed simultaneously.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] Figure 1 is a block diagram illustrating the steps of an early mug lti-
electrode
system showing that an operator makes changes to the system settings before
the
actual experiment can commence.
[0050] Figure 2 is an illustration showing a procedure in which an operator
must
configure and reconfigure the stimulation sites and stimulation parameters
prior to
beginning the actual experiment.
[0051] Figure 3 is a block diagram illustrating the steps of a mufti-electrode
system having a controller for automatically selecting the stimulation sites
and
configuring the stimulation parameters.
[0052] Figure 4 is an illustration showing a procedure in which the
stimulation
sites and stimulation parameters are automatically configured prior to
beginning the
actual experiment.
[0053] Figure SA is a bloclc diagram of a mufti-electrode device architecture.
[0054] Figure SB is a block diagram of a mufti-electrode device archit ecture
having two levels of controllers.
[0055] Figure 6 is a block diagram of a controller.
[0056] Figure 7 shows exemplary circuit diagrams for the controller digital
motherboard.
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[0057] Figures 8A-8B are exemplary circuit diagrams for controller daughter
boards.
[0058] Figure 9 is a block diagram of an amplifier module.
[0059] Figure 10 is an exemplary circuit diagram for an amplifier digital
motherboard.
[0060] Figures 11-12 are exemplary circuit diagrams for amplifier daughter
boards.
DESCRIPTION
[0061] Central to the system described here and the process of using it is the
placement of a controller between a computer and a multielectrode probe for
monitoring electrophysiological activity of a tissue slice placed on that
probe. In
particular, the controller switches (or selects) the electrodes to sense
electrical activity
at various tissue sites of the tissue slice. The controller may also be
configured to
activate one or more electrodes with a stimulating signal, thereby stimulating
corresponding tissue sites. A computer is typically used to instruct or
program the
controller to carry out the selecting and switching process. Also, because of
the low
level of signal found in the neural tissue, an amplifier module is preferably
introduced
between each probe and the controller to amplify or otherwise condition the si
finals
arising from the tissue.
[0062] Figure 3 shows in block diagram fashion, the manner in which the
controller allows the computer to aid the analyzer and operator to choose
appropriate
slice position and parameters according to the particular analysis desired.
The
controller selects the tissue sites to monitor and stimulate without input
from the
operator.
(0063] As shown in Figure 4, the use of a controller to select a specific
probe to be
measured and software to measure, to compare, and to select (or not) the
specific
probe and as necessary, to adapt the stimulation parameters for a specific
site, allows
elimination of the manual review and selection step shown in Figure 2. In
particular,
Figure 4 shows that, in a situation where a series of experiments are to be
run, the
operator or technician performs only the initial set-up. In these types of
experiments,
the experience hand of the operator needed to set up the experiment is
substari.tially
lessened.
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[0064] For example, assuming that on average it takes one minute to physically
place a brain slice on the experimental platform and 10 minutes to select
stimulation
sites and to configure stimulation parameters, then using the device offered
in Figure 1
requiring human intervention during the configuring phase, the maximum number
of
experiments that a single technician can start is no more than six per hour.
Using the
system described in Figures 3-4, on the other hand, it would theoretically be
possible
to start up to 60 experiments per hour since the time-limiting step for the
technician is
the step of placing the brain slice on the right place of the multi element
probe
indicated by 'O' in Figure 4.
[0065] Use of the procedures and devices described just above further allows
the
implementation of highly complicated and sophisticated protocols. For
instance, the
design of protocols, for instance, those requiring complex stimulation
patterns, in
which the stimulation of several independent sites is needed, may be achieved
with
but a small time delay between stimulations. In early multi-electrode
physiological
tissue monitoring systems, due to the fact that a human operator is required
to set the
stimulation site, the shortest time between stimulations is limited by the
speed of the
human in doing the actual switching from one site to another. Using the
described
devices and procedure, on the other hand, the switch may be made in
milliseconds,
malting it possible to observe the evoked response of a network of neurons
when those
neurons are stimulated from different sites within a short time period. Since
such
brain natural phenomena occurs within the time constraints of the natural
events in the
brain, it is important to be able to mimic the same complex stimulation
patterns in
order to investigate realistic behavior.
[0066] The described procedure and hardware may be used to significantly
reduce
the cost of achieving high throughput on mufti-electrode experiments by
reducing the
number of hardware elements. In using the procedure shown in Figure l, a
conventional architecture, to increase throughput by a factor of N X N
independent
systems, each requiring a computer, amplifier, and additional devices, as well
as some
number of technicians are needed. Using the procedures and designs
corresponding to
Figures 3 and 4, on the other hand, reduces the complexity and cost by
requiring but a
single computer and simple modules, all potentially managed by a single
technician.
[0067] Mufti-experiment studies, for example, dosage-response studies may be
optimized by, for instance, combining the results of several experiments
running on a
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single system using the described procedures and devices and reconfiguring
each
experiment as a function of the results of experiments.
[0068] A basic system, not enhanced using the instant device and procedure,
includes a mufti-electrode array (a "MED-Probe"), an analog amplifier (a "MED-
amplifier"), and the computer containing the analog-to-digital connector ("A/D
converter") and appropriate software.
[0069] The system described herein comprises two basic hardware components: a
DS-MED controller and a dedicated DS-MED amplifier module for each probe. The
DS-MED amplifier module may be, as described further below, an amplifier
device
comprising multiple circuits and boards for receiving, distributing, and/or
conditioning signals.
[0070] The DS-MED controller is connected to the system amplifier and emulates
the behavior of a MED probe connected directly to the system amplifier. The
controller is also connected to two buses, a Control Bus and an Analog Signal
Bus. If
a controller. switches amongst, e.g., eight channels, each switched channel
will include
a DS-MED amplifier module for each probe. The control bus selects a probe or
channel amongst those accessed by the DS-MED controller. Once so selected, the
signal emitted by the probe is amplified by the channel DS-MED amplifier
module,
the so-amplified signal passes through the analog signal bus, passes through
the DS-
MED controller, the MED or system amplifier and onto the computer. Both the
control bus and the analog bus are shared with each of the accessed DS-MED
amplifier modules. In addition to being connected to the control and signal
buses, the
amplifier modules are directly connected to the MED probes. As shown in Figure
Sa,
each amplifier module manages a single probe.
[0071] Furthermore, each probe includes a plurality of electrodes. The
electrodes
sense electrical activity in a tissue slice placed on/in the probe. The
electrodes or
tissue sites may be activated/stimulated by, for example, sending a
stimulation signal
to the electrodes. For example, a voltage potential may be applied between two
or
more electrodes. The DS-MED controller can be configured to automatically
select
electrodes to monitor and to activate. In this manner, the electrode
monitoring and
stimulating parameters may be configured for experiments relatively quickly.
Additionally, by connecting multiple probes to a single controller and
computer,
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multiple tissue slice experiments may be configured and run in parallel using,
for
example, time-multiplexing software.
[0072] In more complex configurations a primary amplifier can be used to
manage
one or more daughter controllers, which daughter controllers in turn can be
connected
to a group of amplifiers, and so on. In this way hierarchical configurations
of many
controllers and probes can be built. Figure Sb shows an example of a multi-
level DS-
MED architecture.
[0073] Further details of the DS-MED controller and amplifier module are
described below.
THE DS-MED CONTROLLER
[0074] The DS-MED controller depicted in Figure 6 includes 10 circuits: one
digital motherboard, one analog motherboard, and eight identical 8-electrode
filtering
banks daughter boards. A block hardware diagram is presented in Figure 6.
[0075] The digital motherboard contains a microprocessor running a low-level
program for controlling the DS-MED amplifier modules which are connected to
the
control and analog signal busses as well as the communication with the DS-MED
software running on the computer. The microprocessor sends commands,
addresses,
and operands to the DS-MED amplifier modules through the control bus. It also
manages the communication to the computer and implements commands sent to it
by
the latter. These commands are used to 1) configure the individual DS-MED
amplifier modules, 2) select one of the available stimulation sources (e.g.,
there may
be four or more sources), and 3) select the specific high frequency filter on
the eight 8-
electrode daughter boards. As shown in figure 6, a serial port, a clock and
the
stimulation selection circuitry can also be included in the DS-MED controller.
[0076] Finally, an interface may be included in the controller makes it
possible to
download new versions of the low-level program to run in the microprocessor
and in
this way reprogram and extend the functionality of the DS-MED controller in
particular and the DS-MED architecture in general. An example circuit diagram
is
shown in Figure 7.
[0077] The analog motherboard contains the interface between the analog signal
bus and the inputs to the 8-electrode daughter boards, and between the output
of these
and the connector to the MED or system amplifier.
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[0078] The eight 8-electrode daughter boards may each contain a set of high
frequency filters and conditioning amplifiers, one set for each electrode. The
filters
are used to allow the A/D data acquisition cards to sub-sample the
electrophysiological signals and in this way reducing the amount of data that
has to be
stored per experiment. The conditioning amplifiers make it possible to match
the
electrical characteristics of the analog signals to the requirements of the
MED
amplifier. Example circuit diagrams are shown in Figures 8A and 8B.
THE DS-MED AMPLIFIER
[0079] The DS-MED amplifier module shown in Figure 9 may have 10 circuits: a
digital motherboard, one analog motherboard, and eight daughter boards. A DS-
MED
amplifier block diagram is shown in Figure 9.
[0080] The digital motherboard for the DS-MED amplifier module typically
includes circuitry to 1) identify uniquely each amplifier, 2) decode the
address sent
from the controller, 3) respond to the read and write commands from the
controller, 4)
maintain the state of probe, and 5) distribute the stimulation signal to the
electrodes
(e.g., to the 64 electrodes) through their respective daughter boards. A
corresponding
circuit diagram is shown in Figure 10.
[0081] The analog motherboard for the DS-MED amplifier module typically
includes an interface between the MED probe and the inputs to the 8-electrode
daughter boards, and between the output of these and the analog signal bus. An
example circuit diagram is shown in Figure 11.
[0082] The eight 8-electrode daughter boards contain a bank of head amplifiers
that condition the analog signals coming from the MED probes in order to
transfer
them without significant distortion to the analog signal bus. There is also
circuitry to
allow each electrode to function either as a recording or a stimulation
electrode and to
transfer the stimulation signal to the probe. The circuit diagrams are shown
in Figures
11-12.
[0083] The above described DS-MED architecture provides for a number of
advantages and benefits. The described procedure may provide, for example,
flexible
architecture scales. That is to say that a wide variety of systems are
possible using the
described devices and procedures. For instance, the described device may be
used to
build a simple single probe, or a 1-dimensional system with N probes, or more
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complex systems, e.g., two dimensions in which a controller manages several 1-
dimensional systems, each with some number of probes. The described system may
also provide modularity. By combining the described components, we are able to
build a system having an arbitrary number of probes under the control of a
single
computer or several systems each with a smaller number of probes, each
connected to
a single computer. This system may further provide automatic selection of one
of a
plurality of MED amplifier stimulators (e.g., 4) and one of a plurality of MED
probe
electrodes (e.g., 64) as a target site for stimulation. Additionally, all
experiments may
run at the same time by time-multiplexing the use of available MED probes
which
may be carried out under the control of software.
[0084] Suitable software may be that known or readily developed by those of
ordinary skill in the art to carry out the procedures and systems described
here.
Preferably, the software provides a convenient user-interface to control
selection of
electrodes and tissue sites to be monitored and activated. For example, the
software
may run a procedure that arbitrarily monitors each and every site as well as
stimulates
each and every site with various stimulation signals. The software also
preferably
facilitates the recording and analyzing of information. For example, the
software may
nm an algorithm that compares measured signals to a threshold value. Still
other
suitable software may be used with the hardware described here.
[0085] The inventive system and procedure provides still other advantages and
benefits. The invention may be embodied in other forms without departing from
the
spirit or essential characteristics thereof. The embodiments disclosed here
are to be
considered only as illustrative and not as restrictive. The scope of the
invention is
found in the appended claims; all changes which come within the meaning and
range
of equivalency of the claims are intended to be embraced therein.
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